Non-contact voltage detectors are well known in the field of electrical work, and are used routinely by electricians, utility workers, homeowners, and others who work near electrical equipment to provide a visual and/or audible indication that an electrical component is energized with electrical voltage. Often, the source of electrical voltage is located in a dark place and difficult to see, such as within a wall, ceiling, or panel box. Thus, it is advantageous for a non-contact voltage detector to include both a means of illuminating the area to be tested and a means to alert the user to the presence of a potentially dangerous voltage.
U.S. Pat. No. 6,924,605 to Chun describes a non-contact voltage detector with a built-in flashlight. The function of the Chun device is typical of current non-contact voltage detector and flashlight devices. When the unit is powered on, both the flashlight and the voltage detector power up, and when the power is turned off, or when the battery gets too weak, both the voltage detector and the flashlight shut down. The device of Chun will remain active until it is turned off, so the operator can rely on its readings during use, which can cause the battery to drain quickly. In the past, attempts have been made to prolong battery life of non-contact voltage detectors, for example, by using automatic power shutoff systems. Such systems, however, can shut-off the detector while the user believes it to be on, which may lead to inaccurate readings.